Atomizer burners are known in which the oil for combustion is finely distributed in a mechanical manner. The oil is broken up into fine droplets of about 10 to 400 .mu.m diameter (oil mist) which vaporize and burn in the flame while mixing with the combustion air. In pressure atomizers (see Lueger-Lexikon der Technik, Deutsche Verlags-Anstalt Stuttgart, 1965, volume 7, p. 600), the oil is fed under a pressure of about 4 to 25 bar to an atomizer nozzle by an oil pump. The oil passes through essentially tangentially running slots into a swirl chamber and leaves the nozzle via a nozzle bore. The oil particles are thereby given two component motions--an axial component motion and a radial component motion. The oil film issues from the nozzle bore as a rotating hollow cylinder, and expands through centrifugal force to form a hollow cone. The margins of the fuel cone, however, start to vibrate in an unstable manner and break into small oil droplets. The atomized oil forms a cone having a more or less large opening angle.
However, in the case of the low-pollution combustion of mineral fuels in modern burners, for example in premixing burners of the double-cone design, which in their basic construction are described in U.S. Pat. No. 4,932,861 to Keller et al., special requirements are imposed on the atomizing of the liquid fuel. These are in particular as follows:
1. The droplet size must be small so that the oil droplets can vaporize completely before combustion.
2. The opening angle (expansion angle) of the oil mist is to be small.
3. The droplets must have a high velocity and a high impulse in order to be able to penetrate far enough into the compressed combustion-air mass flow so that the fuel vapor can premix completely with the combustion air before reaching the flame front.
Swirl nozzles (pressure atomizers) and air-assisted atomizers of the known designs having a pressure of up to about 100 bar are scarcely suitable for this, since they do not permit small expansion angles, the atomizing quality is restricted, and the impulse of the droplet spray is low.
As a consequence of inadequate vaporizing and premixing of the fuel, the addition of water is necessary for lowering the flame temperature and thus reducing NOx formation. Since the fed water also often disturbs flame zones, which certainly produce little NOx per se but are very important for the flame stability, instability such as flame pulsation and/or poor burn-out often occurs, which leads to the increase in the CO exhaust.
An improvement can be achieved with the high-pressure atomizer nozzle disclosed by EP 0 496 016 A1. This high-pressure atomizer nozzle consists of a nozzle body in which a turbulence chamber is formed which is connected via at least one nozzle bore to an exterior space. The nozzle has at least one feed passage for the liquid to be atomized, which can be fed under pressure. The cross sectional area of the feed passage leading into the turbulence chamber is greater than the cross sectional area of the nozzle bore by the factor 2 to 10. This arrangement enables a high level of turbulence to be produced in the turbulence chamber, which does not abate on the way from the turbulence chamber to the discharge from the nozzle. The liquid jet is rapidly disintegrated in the exterior space, that is, after leaving the nozzle bore, by the turbulence produced in front of the nozzle bore, in the course of which small expansion angles of 20.degree. or less result. The droplet size is likewise very small. Only the loss of fuel impulse in the turbulence generator is disadvantageous, which does not permit directed introduction.